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Science 24 April 2009:
Vol. 324. no. 5926, pp. 513 - 516
DOI: 10.1126/science.1168120
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Reports

Catalytic Core of a Membrane-Associated Eukaryotic Polyphosphate Polymerase

Michael Hothorn,1,2 Heinz Neumann,3,* Esther D. Lenherr,1 Mark Wehner,4 Vladimir Rybin,1 Paul O. Hassa,1 Andreas Uttenweiler,3,{dagger} Monique Reinhardt,3 Andrea Schmidt,3 Jeanette Seiler,1 Andreas G. Ladurner,1 Christian Herrmann,4 Klaus Scheffzek,1,{ddagger} Andreas Mayer3,5

Polyphosphate (polyP) occurs ubiquitously in cells, but its functions are poorly understood and its synthesis has only been characterized in bacteria. Using x-ray crystallography, we identified a eukaryotic polyphosphate polymerase within the membrane-integral vacuolar transporter chaperone (VTC) complex. A 2.6 angstrom crystal structure of the catalytic domain grown in the presence of adenosine triphosphate (ATP) reveals polyP winding through a tunnel-shaped pocket. Nucleotide- and phosphate-bound structures suggest that the enzyme functions by metal-assisted cleavage of the ATP {gamma}-phosphate, which is then in-line transferred to an acceptor phosphate to form polyP chains. Mutational analysis of the transmembrane domain indicates that VTC may integrate cytoplasmic polymer synthesis with polyP membrane translocation. Identification of the polyP-synthesizing enzyme opens the way to determine the functions of polyP in lower eukaryotes.

1 European Molecular Biology Laboratory, Structural and Computational Biology Unit, Meyerhofstrasse 1, 69117 Heidelberg, Germany.
2 Plant Biology Laboratory, Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA.
3 Département de Biochimie, Université de Lausanne, 1066 Epalinges, Switzerland.
4 Physikalische Chemie 1, Ruhr-Universität Bochum, 44780 Bochum, Germany.
5 Department of Biochemistry and Molecular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA.

* Present address: Medical Research Council Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH, UK.

{dagger} Present address: Novartis Pharma Schweiz AG, Monbijoustrasse 118, 3007 Bern, Switzerland.

{ddagger} To whom correspondence should be addressed: E-mail: scheffzek{at}embl.de

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
ATP-Dependent but Proton Gradient-Independent Polyphosphate-Synthesizing Activity in Extraradical Hyphae of an Arbuscular Mycorrhizal Fungus.
C. Tani, R. Ohtomo, M. Osaki, Y. Kuga, and T. Ezawa (2009)
Appl. Envir. Microbiol. 75, 7044-7050
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Science. ISSN 0036-8075 (print), 1095-9203 (online)